Stevens said Friday he will step down when the court finishes its work for the summer in late June or early July. He said he hopes his successor is confirmed “well in advance of the commencement of the court’s next term.”

According to NBC News, a senior administration official says the White House received Steven’s retirement letter this morning. The president, traveling back from an overseas trip, was informed aboard Air Force One.

His announcement had been hinted at for months. It comes 11 days before his 90th birthday.

Stevens’ departure from the high court will mark the end of an era: he is the last justice to have served in World War II, lived through Prohibition, and was around for the start of the Great Depression.

In terms of the Supreme Court’s stark ideological divisions, it’s unlikely that Stevens’ retirement will change the makeup of the bench — despite having been nominated by a Republican president (Ford), Stevens is one of the high court’s most reliably liberal votes. President Obama, who Stevens praised in recent interviews, will almost certainly replace Stevens with another progressive voice, keeping the center-left bloc with four votes (joining Ginsburg, Breyer, and Sotomayor).

Obama is scheduled to address Stevens’ announcement in the Rose Garden this afternoon, around 1:20 (ET)*. This will be the president’s second opportunity to fill a Supreme Court vacancy, following last year’s Sotomayor nomination. Several names of jurists have become the subject of D.C. scuttlebutt in recent weeks, and most of the attention has been focused on Solicitor General Elena Kagan, and appeals court judges Diane Wood and Merrick Garland.

As recently as five days ago, Senate GOP leaders were already openly speculating about filibustering the president’s unnamed nominee.